Each genera has some species that produce nectar, and attract insects. The ovary wall has three layers, each of which can develop into a different part of the fruit. There is an incredible diversity of flower structure, not only in the number of sepals, petals, stamens, and carpels, but also in the way these modified leaves are attached with respect to the ovary.
The generative cell is contained within the larger pollen tube cell. Because cross-pollination allows for more genetic diversity, evolution has selected for many ways to avoid self-pollination in different species:.
The other sperm nucleus fuses with the fused polar nuclei to make a triploid cell. Living gymnosperms are a diverse group of plants, most of which bear their sporangia in large, prominent strobili or cones. In India, Japan, and Sri Lanka, sago flour is often made from cycad stems it is also made from real palms, which are angiosperms.
One is the tube cell, the other will act as a sperm. Share Flipboard Email.
Their needle-shaped leaves are also an adaptation to conserve water. It also means that pollen grains, which are abundant in the fossil record, allow us to reconstruct ancient plant communities, and these communities in turn tells us about ancient climates. Individuals who are well-adapted to current conditions may not be well adapted if and when conditions change; therefore, genetic diversity is beneficial in changing environmental or stress conditions this is the main advantage of sexual reproduction , after all!
These wings were presumed to aid in wind pollination, but recent evidence suggests they help the pollen grain float up through the micropyle to the egg. All of these differences can affect the final physical appearance of the fruit.
Fruits and seeds are dispersed by various means. The evolutionary innovation of the seed is analogous to the evolution of the amniotic egg in reptiles. The base of the flower is called the receptacle , and the tiny stalk that holds it is the pedicel.
Also available from Amazon , Book Depository and all other good bookstores. The competitive success of angiosperms is partly due to animal pollination, which allowed angiosperms to exist as small scattered populations.
Growth form of ferns Ferns grow in a massive variety of forms, from trees to vines to shrub-like plants. The mechanism of pollination and the features of the flower are tightly linked:. Plant Reproduction. Welwitschia has a single species, W.
But in all other habitats, flowering plants rapidly became the dominant plant life.